The theory behind the change in diet is to "starve out" the candida so they will not reproduce and will eventually die out.
The natural chemicals in the herbs that will kill the candida do not care what you have eaten. They will work if you have eaten a carrot or a Big Mac.
The best way to treat candida is just to kill all of it from all over the body. The body will reset itself with the proper amount it needs from the foods that you eat.